November 23, 2020
The 2020 holiday season is just around the bend, and while our social habits have changed drastically during the COVID-19 pandemic, one thing remains the same: The desire to spend quality time with our loved ones.
But holiday celebrations and other forms of indoor socializing come with significant safety risks. When we welcome guests for joyful gatherings around the dining room table, we might also open the door to an uninvited visitor – SARS-CoV2, the virus that causes COVID-19 infection.
What can we do to make our homes safer, and keep our families healthier, now and into the New Year? First, avoiding indoor social gatherings is always safest. Another major step we can take is to pay attention to the air quality in our living spaces. “The virus lingers in the air. That’s a key point for people to understand,” says Paula Olsiewski, PhD, Contributing Scholar at the Johns Hopkins Center for Health Security. “It is often spread by apparently healthy but infected people, who shed it with every breath.”
Olsiewski, who is Chair of the U.S. Environmental Protection Agency (EPA) Homeland Security Research Subcommittee and has expertise in the science of indoor air quality, spoke to SAA and offered valuable advice you can follow to reduce the risk of transmission at home.
How can we avoid breathing unsafe air and lower our risk of getting COVID-19?
Although the CDC continues to recommend social distancing and limiting contact with people who don’t live in your household, many may choose to host or attend gatherings this winter nonetheless. “Ideally you want to avoid other people who don’t live with you,” Olsiewski says. “But people are lonely, they haven’t seen their families in a while – it’s been a really hard time for people. So here are some things you can do to reduce your risk, whether or not you’ll be welcoming loved ones into your home this holiday season.”
- Wear masks at all times, indoors and outdoors, except when at home with the people you already live with.
- Everyone, including children age two and above, should wear a mask.1
- Try to avoid being within six feet of other people and keep exposure as short as you can – masks are not a substitute for social distancing.2
- The higher the local infection rate, the higher the number of apparently healthy people shedding virus in your community – so be aware of increased risk as you plan your holiday activities.
What type of mask is best? We see a range of different kinds – neck gaiters, bandanas, cloth masks, surgical masks, and N95s. What is most appropriate for indoor social gatherings?
N95 masks offer the most protection, but are only needed in very high-risk situations, such as if you’re a healthcare provider, Olsiewski says. Otherwise, if everyone just wears a cloth mask with two or more layers of fabric, it cuts down virus transmission.1
“The best mask for a person is the one they will keep on,” she says. Uncomfortable or ill-fitting masks can lead a person to wear the mask improperly, reducing its effectiveness – so she encourages everyone to wear one that is comfortable.
Are there specific hot spots in the home where infection between people may be more likely? And how can we better protect those rooms or areas?
Hot spots occur anywhere people are clustered together, according to Olsiewski. That’s because the virus is mainly spread via respiratory droplets produced when an infected person coughs, sneezes, laughs, or talks.
But what many people don’t realize is that these droplets can linger in the air for far longer than first believed. Small, airborne microdroplets are now being studied as a third mode of virus transmission (after larger respiratory droplets and contact with contaminated surfaces).3
“Let’s say I’m infected. If I’m sitting quietly, I’m exhaling virus particles. If I’m eating and talking and laughing, it goes farther and farther,” Olsiewski says. “If your voice and your breath are going far, the virus is being carried with it.”
One of the dangers of holidays like Thanksgiving and Christmas is that when people sit down together for a meal, they must take off their masks to eat, removing their protection against such droplets. If you’re eating with others indoors, put your mask on again as soon as you’re done eating, Olsiewski cautions.
For good measure, you should also be prepared to bring extra masks and hand sanitizer with at least 60% alcohol to a holiday gathering, in case supplies are lacking, according to the CDC.2 And be mindful that if the group celebrates by singing songs, the chances of spreading the virus get higher and masks are especially vital.
“You don’t know who has COVID-19, and that’s where the danger comes from,” she says. “And if someone has it, it can just be lingering in the air in your home, or the gym, or the movie theater – anywhere.”
How can we make the indoor air in our homes cleaner and safer?
Olsiewski promotes the benefits of two methods: ventilation and filtration. “How do you clean your air? You either dilute it or filter it. This doesn’t eliminate the risk if someone is sitting in your home breathing out the virus. But it does reduce the risk.”3
It’s crucial to keep air moving in your home4 – and there are several ways to do it.
- If your home has mechanical ventilation – a central heating and air conditioning system that moves air through ducts – do the following:
- Install a higher efficiency filter in your system, MERV 13, if possible.
- Set the fan to “on” instead of “auto” so that the air in your home continuously passes through the filter.
- Add a HEPA portable air cleaner and a room humidifier.
- If your home has natural ventilation – windows that open, room air conditioners, and radiators for heating – do the following:
- Open windows to increase ventilation and make sure you can feel a cross breeze.
- Add a HEPA portable air cleaner and a room humidifier.
How is a HEPA air cleaner better than using a standard portable fan to move air around?
“A HEPA removes particles from the air, including the particles that the virus is riding on as it lingers,” Olsiewski says. “A fan can be effective if it blows the air out a window, but it also might just blow the air around.” A portable air cleaner with a HEPA filter can help reduce the risk of airborne transmission of the virus.5
Buy a HEPA portable air cleaner that matches the size of the room where you plan to use it and run it continuously, especially on the highest setting, when others are in your home, she says.
Check any filter manufacturer’s website for specs that can help you determine what you need based on the size of your room, and the square footage you are trying to clean.
You can also make an economical DIY filter using a box fan and MERV 13 furnace filter – the directions can be found here.6
Olsiewski also says to avoid air cleaners that are ionizers or use ozone, as the data are lacking on their effectiveness.
What else can we do to improve air quality in our homes this winter
Using a humidifier is another helpful step we can take, Olsiewski says. “Humidifiers are important because in dry air, the virus lasts longer, and people are more susceptible to infection,” she notes. Ideally, the relative humidity inside a house should be between 40% and 60%.7
“People are less likely to get a respiratory infection in this range,” she says. That’s because the respiratory immune system more effectively captures and removes germs under these conditions.7
How can we monitor the humidity in our homes, and how often should we use a humidifier?
Sensors are available to measure relative humidity (RH) and carbon dioxide (CO2). Carbon dioxide is exhaled during breathing and is not dangerous at levels under 1,000 ppm (outdoor air levels of CO2 hover around 400 ppm). “If you use RH and CO2 sensors, you can take action based on the reading,” Olsiewski says. “For example, if the RH levels are low – which is common indoors during winter – you can add humidity. If the CO2 levels are rising, you can open a window or use a fan to blow out the stale indoor air.”
Outside the home, people may still be nervous about activities like grocery shopping, picking up food from a restaurant, or having a doctor’s visit. Are indoor business spaces generally doing a good job keeping their air clean?
Many indoor businesses don’t know how to properly address indoor air quality because the WHO and the CDC didn’t recognize the virus as airborne until recently, Olsiewski says. “Most guidance just says to increase ventilation. We’re asking buildings to go back to a time when they were designed to circulate outside air – before mechanical ventilation systems,” she explains. “I think most businesses are really trying.”
In the meantime, she offers this advice: “If you really need to schedule an indoor activity – such as a hair appointment, shopping, religious service, etc. – go early or get the first available appointment of the day, and make sure the place requires everyone to ‘mask up.’”
Any other takeaways that we should keep in mind to stay safe this season – or anytime?
Olsiewski uses two metaphors to illustrate the risk of transmitting COVID-19 indoors.
First, indoor risk vs. outdoor risk: “It’s the difference between someone peeing in the hot tub and peeing in the ocean. In the hot tub, it’s pretty bad. In the ocean, it doesn’t affect you as much,” she says with a chuckle. “Outdoors, the air is more diluted. Indoors, it’s not.” That’s why it’s important to maintain proper distance between people – to increase dilution of the air in a small space.
Second, think of the virus staying in the air like this: “If someone was smoking in a room, you would know they were smoking in that room. The virus lingers like that,” she says. If you minimize the number of people potentially breathing out virus particles – and make sure everyone is wearing a mask – the space will be safer.
Dilution, ventilation, and filtration – these three elements, Olsiewski says, can help everyone keep their air as clean as possible and their families protected through the holidays and beyond.8